By-Pass Airflow

During cold engine condition, idle speed control by-pass air increases idle speed to quickly warm engine. The idle speed control by-pass air is made up of thermo-type wax and spring loaded valve assembly. At engine temperatures below 140°F (60°C), thermo-wax is contracted and valve is open. As engine gradually warms to operating temperature, thermo-wax expands and moves valve towards the closed position. The valve is fully closed at engine temperatures above 140°F (60°C).

By-pass airflow also controls amount of by-pass air delivered to intake plenum, ensuring proper idle speed for all operating conditions. Required amount of by-pass air is determined by position of vane airflow meter.